This invention relates to a method of producing a semiconductor device by growing epitaxially a compound semiconductor layer on an element semiconductor substrate crystal, and more particularly to a method of producing a semiconductor device by forming a compound semiconductor layer on a single element substrate such as Si or Ge.
Recently, semiconductor lasers and HEMTs (High Electron Mobility Transistors) have been fabricated by forming a compound semiconductor layer on a Si or Ge substrate by low temperature growth using MOCVD (Organometallic Chemical Vapor Deposition) or MBE (Molecular Beam Epitaxy).
The reasons why Si is used recently for the substrate are as follows:
(i) Si is economical.
(ii) An extremely large dislocation-free substrate can be produced in comparison with a GaAs substrate and an InP substrate.
(iii) A hybrid OEIC (Optoelectronic Integrated Circuit) can be obtained by forming in advance a device on the Si substrate and then a GaAs device, for example, on the former.
(iv) In the item (iii) described above, a device capable of optical communication between wafers can be obtained by forming a laser or a light emission diode and a photo-detective element by GaAs or InP, for example.
The reasons why Ge is used for the substrate are the same as Si. In addition, since Ge has extremely good lattice matching with GaAs at room temperature, it is suitable for GaAs system devices. Furthermore, InP/Ge, too, has better lattice matching than InP/Si because the lattice mismatching of the former is 1/2 of the latter. Therefore, Ge is suitable for forming InP system devices, too. However, the resulting Ge wafer is smaller than the Si wafer.
When a GaAs layer is grown epitaxially on a Ge substrate or a Si substrate on which Ge is grown epitaxially, autodoping of Ge into the epitaxial growth layer becomes problems. If the GaAs layer is grown directly on the Si substrate, crosshatchlike misfit dislocations are likely to occur. In addition, a kind of twin structure called "Anti-phase Domain" is likely to occur because the binding force is greater between Ge or Si and As or P than between Ge or Si and Ga or Al, or the like, and because of ruggedness and steps on the surface.
No prior art reference relating to, or analogous to, the present invention can be found to the best knowledge of the present inventors.